H3lp with resizing VM raw disk

Hi people I´m using kvm and I decide 2 increase yhe HD of a VM I use the command
qemu-img resize <VMID-Hard Drive.raw> + 20G
so the original hard drive file was about 100 GB so it becomes 120G but it did´nt instead when I check it
ls -lh

I see this:

-rw-r--r-- 1 root root 20G Jan 31 08:02 vm-100-disk-1.raw

I can´t understand this can anyone help???? What happen 2 this

Thank in advance Stryder